This project will develop and apply a comprehensive set of quantitative methods for assessing medical technologies. Specific aims are (1) to develop a comprehensive set of methods for analyzing and combining evidence from different sources. This will include the development of formulas that describe the information in a piece of evidence for controlled trials, case- controlled studies, cross-sectional studies, and a small subset of longitudinal studies; (2) the extension of these formulas to enable adjustment for biases affecting internal and external validity; (3) the development of quantitative models to identify and estimate the magnitudes of biases; and (4) the development of formulas to combine the results of different pieces of evidence. The project will also develop quantitative methods for setting research priorities and for selecting medical technologies for assessment. Prototype computer software will be developed to implement the formulas and models described in aims 1-3, and the methods will be applied to assess at least four medical technologies.